(a) Field of the Invention
This invention relates to an insufflation unit for use in endoscopic operations and in particular in human medicine, in which a gas which is introducible into a body cavity such as the uterus from a gas supply device via an instrument channel in the endoscope is monitored for pressure and flow rate and can be fed through a filter-equipped extractor circuit to filter out smoke and/or vapor.
(b) Description of the Prior Art
Units of this kind are needed to distend in the requisite manner a body cavity which is to be examined and treated in the course of an endoscopic operation. At the same time it is necessary that the pressure inside the body cavity should be kept as constant as possible during the operation.
It is known from DE-OS-3739003 (U.S. Pat. No. 5,013,294) to provide an insufflation unit with two flow paths and which is able constantly to compensate for minor losses of gas. Larger losses of gas, which may be be caused by a change of instruments or the like, can quickly be compensated for by changing over to the second flow path before the preselected lower pressure limit is reached. It is also ensured that, should the preselected upper pressure limit be overrun, the supply line and pump and any other ancillary devices which are connected to the outlets and operated by the analyser electronics are switched off and no more gas is fed into the body cavity.
DE-PS 3329784 (U.S. Pat. No. 4,538,594) discloses another unit of this kind which is suitable for use with coagulating instruments such as lasers. In this case there is a requirement that the smoke produced during the coagulation should be withdrawn as quickly as possible because it hampers the visual monitoring of the operation, and the withdrawal process must be carried out without the pressure in the body cavity changing. In the present prior art device this is done by extracting the smoke together with secretion and insufflation gas, the gas being cleaned by a filter and fed back into the body cavity in closed circuit.
Known insufflation units which have high gas flow-rates to produce the desired fast correction of pressure are not suitable for endoscopy in small body cavities like the uterus because in this case it is important for the maximum infeed of gas which is acceptable under the given physiological conditions not to be exceeded.
The main object of the present invention is to overcome the disadvantage that the said insufflation units are not suitable for operations of the kind mentioned hereinabove.